Comparative potencies of contemporary generic vancomycin lot: in vitro assay results from nine products and a reference reagent-grade sample.

Numerous studies of generic vancomycin (GV) lots have emerged since the 1980s, casting some doubt on product quality. Publications question the in vivo activity, even when concurrent in vitro and chemical assays meet regulatory guidelines. This study assessed contemporary GV lots by an in vitro assay capable of measuring small variations from target-benchmark (BM) activity. Nine GV lots (Hospira [6 lots; 0.5- or 1.0-g vials], Akorn [1 lot; 1.0-g vial], APP [2 lots; 1.0-g vials]) were obtained from local United States distributors. A reagent-grade lot (Sigma lot 080M1341V) was tested as BM component due to the inability to purchase branded product vials in the USA. All lots of GV did not vary significantly from the analytical control when testing the 3 Staphylococcus aureus (wild-type 4B25, ATCC 25923, and 29213) and Enterococcus faecalis (ATCC 29212) strains. These MIC end points were read at 18 h of incubation, and Hospira lots averaged +3.5% potency (range, -3% to +8%), and Akorn and APP at 0% variance, e.g., acceptable performance. In conclusion, with a validated, precise multi-organism assay, current GV lots marketed in the USA showed minimal activity variations from a selected BM control lot. Generic antimicrobial products, in general, should be regularly monitored for potency, chemical purity, and in vivo activity before routine use in medical centers.